The invention relates to an independent suspension of a wheel of a two-track vehicle. Such an independent suspension is disclosed, for example, in WO 2011/072967 and U.S. Pat. No. 5,620,173.
Independent suspensions of the inventive type are used especially for the rear axles of automobiles. In the case of such rear axles, the wheels are normally not steerable and, as is correspondingly known, have a great influence on the driving stability and driving safety of the vehicle. In order to attain stable driving handling in the greatest possible number of driving situations, modern rear axles are kinematically designed such that they generate a negative camber angle via the spring compression travel. The negative camber angle maximizes the transferable lateral forces relative to the vehicle structure or vehicle body. In addition, a toe-in angle at the wheel is desired in terms of the kinematic effects via the spring compression travel of the wheel relative to the vehicle body and in terms of the elastokinematic effects via the longitudinal forces acting on the wheel (in particular during deceleration) in order to generate understeering handling of the vehicle and to prevent the rear from suddenly breaking away when there is a change in the load. Today there are relatively complex axle designs for such handling, for instance in the form of five link axles or semi-trailing arm axles. However, in addition to high costs, these axle designs also suffer from the drawback that they require a lot of installation space. In contrast, torsion beam rear axles, which are also known, are somewhat less expensive but have certain drawbacks with respect to driving dynamics.
Known from WO 2011/072967 is an independent suspension of a non-steerable wheel of a two-track vehicle in which a trailing arm supports, on its rear end with respect to the direction of travel, an associated wheel. The trailing arm is furthermore hinged at its front end area to the vehicle structure by way of a pendulum link, and in its center area to the vehicle structure by way of a scissors-type arm.
The aforesaid U.S. Pat. No. 5,620,173 describes an independent suspension in the form of a so-called double-acting distributed pressure vibration-proof structure, which may apparently be provided between the structure and the axis of a vehicle.
The object of the invention is to provide an independent suspension that requires an especially small installation space and yet leads to precise wheel guidance at the required angles in order to attain, in particular, stable driving handling over the greatest possible number of driving situations.
This and other objects are achieved in accordance with the invention by an independent suspension of a wheel of a two-track vehicle having a trailing arm that at one end area is hinged to a body of the vehicle and at its other end area supports a wheel carrier. A scissors-type arm is hinged to the trailing arm and guides the trailing arm relative to the vehicle body. A spring element supports the trailing arm relative to the vehicle body, wherein the spring element is arranged on the trailing arm in the region of the hinge point of the scissors-type arm to the trailing arm when viewed in the direction of the vehicle longitudinal axis.
The scissors-type arm is hinged to the trailing arm inside the wheel rim in a lateral projection of the wheel rim. In one particularly advantageous refinement, the scissors-type arm may be arranged overall inside the wheel rim or in this rim interior space in a lateral projection (but only when seen from a lateral projection).
The hinging of a scissors-type arm to a trailing arm of an independent suspension makes optimum use of the space available on the associated wheel. The hinging is embodied such that it is disposed in a hollow space formed by the rim or in the immediate lateral projection of said hollow space. Thus the scissors-type arm may also be arranged in this area, so that it fits into the available installation space particularly advantageously. The result is an especially compact manner of construction combined with short lever lengths and low transverse force effects. Moreover, the manner of construction has a positive effect on the vehicle body and especially permits a particularly low volume for the wheel house here.
Such a design of the scissors-type arm overall provides a compact construction that nevertheless permits sufficient excursion of the trailing arm. Furthermore, this design leads to advantageous support of the trailing arm, wherein in particular low bending forces act thereon. Guidance by way of the scissors-type arm and the support force are concentrated on a single force introduction area on the trailing arm.
The aforesaid spring element may be a coil spring. The coil spring makes it possible to have a spring element that is limited to a comparatively small and essentially cubic volume. The spring element may be arranged overall inside the rim in a lateral projection thereof. Such a design creates overall a compact manner of construction that nevertheless permits precise guidance and simultaneously sufficient excursion and resilient support of the trailing arm.
In the independent suspension in accordance with the invention, a damper that supports the trailing arm relative to the vehicle body is also preferably provided and is arranged on the trailing arm in the area behind the scissors-type arm as seen in the direction of the vehicle longitudinal axis.
This type of arrangement of a damper supporting the trailing arm on the vehicle body also leads to a very compact manner of construction. It both enables a longitudinal movement path for the damper and permits the use of a particularly narrow damper body.
The slight mobility of the scissors-type arm in the direction of the vehicle longitudinal axis and, in particular, also the guidance of the trailing arm in the direction of the vehicle transverse axis, is preferably created with a pendulum support hinged to the vehicle body.
In this refinement, the scissors-type arm is guided by a pendulum support that itself is hinged to the vehicle body. The pendulum support extends in particular essentially vertically. It may swing in the direction of the vehicle longitudinal axis and thus permits the scissors-type arm to move slightly in the direction of the vehicle longitudinal axis. In this manner, as already mentioned in the foregoing, the scissors-type arm may compensate the offset that it experiences when the trailing arm is pivoted essentially about the vehicle transverse axis when the wheel compresses and rebounds.
When the associated wheel compresses and rebounds due to the centrally acting weight of the vehicle body and the contact surface of the wheel, which is laterally offset relative thereto, the trailing arm of the inventive independent suspension would travel outward in the direction of the vehicle transverse axis and would possibly rotate about the vehicle longitudinal axis. Guidance that counters this otherwise occurring movement of the trailing arm may be advantageously provided with a pendulum support that is hinged on one hand to the vehicle body and on the other hand to the scissors-type arm. The scissors-type arm is then itself hinged to the trailing arm. The pendulum support may advantageously be designed with two pendulum arms, of which one may be designed in the shape of a triangle and, with its three pivot points, may thus also absorb a torque transverse to the pendulum movement.
Alternatively, the slight mobility of the scissors-type arm in the direction of the vehicle longitudinal axis and in particular also the guidance of the trailing arm in the direction of the vehicle transverse axis is created with a cardanic support hinged to the vehicle structure.
A cardanic support or suspension is a device for rotatably bearing an article in two axes that are essentially at right angles to one another. The inventively used cardanic support represents a very compact design for the independent suspension. It permits the hinging of the scissors-type arm to be slightly displaced in the direction of the vehicle longitudinal axis. At the same time, it supports a torque of the trailing arm about the vehicle longitudinal axis. Thus, in particular, it prevents the trailing arm from twisting about its longitudinal axis. In addition, the cardanic support is preferably designed with two axes that are essentially perpendicular to one another and are oriented essentially transverse to the vehicle longitudinal axis. It is particularly preferred that the cardanic support is designed with a cardanic ring that is held with two arms that essentially extend in the vehicle transverse direction such that it is slightly displaceable in the vehicle longitudinal direction. The ring is essentially borne rotation-fast about the vehicle longitudinal axis. A transverse axis is disposed in the ring and the scissors-type arm is hinged thereto. The scissors-type arm is thus borne rotation-fast about the vehicle longitudinal axis and with it the trailing arm. Nevertheless, the scissors-type arm is slightly mobile in the vehicle longitudinal direction. In this manner the pivoting of the inventive trailing arm is very advantageously guided on the vehicle structure in the direction of the vehicle transverse axis and also in the direction of the vehicle vertical axis.
Guidance for the trailing arm in the direction of the vehicle transverse axis is preferably also created with the aforesaid cardanic support. To this end, it is particularly preferred that one of the two axes of the cardanic support is oriented essentially in the direction of the vehicle vertical axis. The scissors-type arm, and with it the trailing arm, is held laterally with this axis. Furthermore, preferably the other axis of the cardanic support is essentially oriented in the direction of the vehicle transverse axis. With this axis the scissors-type arm hinged thereto may pivot up and down and also thus guide the trailing arm.
In other words, the pendulum support or the cardanic support is preferably supported on the scissors-type arm by way of a pivot axis that extends essentially in the direction of the vehicle transverse axis. The angle of this pivot axis to the vehicle transverse axis is advantageously selected to be in the vehicle longitudinal axis/vehicle transverse axis plane in a range between −10° (angle from the vehicle transverse axis to the rear) and +6° (angle from the vehicle transverse axis forward), preferably between −5° and +1°, particularly preferably between −3° and −1°. Furthermore, the angle of this pivot axis to the vehicle transverse axis is preferably selected to be in the vehicle vertical axis/vehicle transverse axis plane in a range between −15° (angle from the vehicle transverse axis downward) and +15° (angle from the vehicle transverse axis upward), preferably between −10° and +10°, particularly preferably between −5° and +5°.
The pendulum support or the cardanic support is furthermore preferably arranged overall inside the rim in a lateral projection thereof.
Such a design creates overall a compact manner of construction that nevertheless permits precise guidance and simultaneously sufficient excursion of the trailing arm.
For guiding the trailing arm in the direction of the vehicle vertical axis, the scissors-type arm is advantageously hinged to a pivot axis that is on the trailing arm and that extends essentially in the direction of the vehicle transverse axis.
The pivot axis of the scissors-type arm, which pivot axis extends in the direction of the vehicle transverse axis, on the trailing arm absorbs the torque or tilt moment that acts essentially about the longitudinal axis of the trailing arm and that occurs when the trailing arm is loaded on the one hand by the contact force of the wheel and on the other hand by the weight of the vehicle. The angle of this pivot axis to the vehicle transverse axis is advantageously selected to be in the vehicle longitudinal axis/vehicle transverse axis plane in a range of between −9° (angle from the vehicle transverse axis to the rear) and +3° (angle from the vehicle transverse axis forward), preferably between −6° and 0°, particularly preferably between −4° and 0°. The angle of the pivot axis to the vehicle transverse axis is advantageously selected to be in the vehicle vertical axis/vehicle transverse axis plane in a range between +3° (angle from the vehicle transverse axis downward) and −2° (angle from the vehicle transverse axis upward), preferably between +2° and −1°, particularly preferably between +1° and 0°.
For the angles, the vertices of the angles are each disposed on the inside of the vehicle and the angles are each open toward the outside of the vehicle.
The hinging of the trailing arm at the first end area to the vehicle structure is preferably created by use of an elastomer bearing that permits an elastokinematic relative movement.
Such an elastomer bearing permits a pivot movement by the trailing arm in the direction of the vehicle vertical axis and furthermore at least a slight degree of freedom in the direction of the vehicle transverse axis. In contrast, the trailing arm is held essentially stationary for its pivot movement up and down on the vehicle in the direction of the vehicle longitudinal axis.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.